Fix flaky test exception in HttpServerTest (#11164)

Fix flaky test exception by closing response in HttpServerTest

DD_C0320J

Co-authored-by: janhavis <janhavi.sahasrabuddhe@gmail.com>

Close response body in redirect and blocking tests to prevent HTTP/2 flow control issues

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Re-add @flaky annotation on test exception until fix is verified in CI

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Merge branch 'master' into dd/fix/pekko-http-flaky-test-exception

Co-authored-by: datadog-prod-us1-5[bot] <266081015+datadog-prod-us1-5[bot]@users.noreply.github.com>
Co-authored-by: janhavi.sahasrabuddhe <janhavi.sahasrabuddhe@datadoghq.com>

Author: janhavis

dd-java-agent/instrumentation-testing/src/main/groovy/datadog/trace/agent/test/base/HttpServerTest.groovy

@@ -1170,6 +1170,7 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     }
 
     response.body().contentLength() < 1 || redirectHasBody()
+    response.close()
 
     and:
     assertTraces(1) {
@@ -1210,6 +1211,8 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     if (bubblesResponse()) {
       assert response.body().string().contains(ERROR.body)
       assert response.code() == ERROR.status
+    } else {
+      response.close()
     }
 
     and:
@@ -1255,6 +1258,8 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     response.code() == EXCEPTION.status
     if (testExceptionBody()) {
       assert response.body().string() == EXCEPTION.body
+    } else {
+      response.close()
     }
 
     and:
@@ -1299,6 +1304,7 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
 
     expect:
     response.code() == NOT_FOUND.status
+    response.close()
 
     and:
     assertTraces(1) {
@@ -1836,6 +1842,7 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     response.code() == 301
     response.header('location') == 'https://www.google.com/'
     !handlerRan
+    response.close()
 
     when:
     TEST_WRITER.waitForTraces(1)
@@ -2117,6 +2124,7 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     }
     response.code() == 301
     response.header("Location") == 'https://www.google.com/'
+    response.close()
     TEST_WRITER.waitForTraces(1)
     def trace = TEST_WRITER.get(0)